CDC: Autism diagnoses growing by 10 to 17 percent annually
The figure is so astounding it appears to be a misprint at first glance.
One in 110.
That's the number of American children living with an autism spectrum disorder (ASD), based on the most recently published estimates from the Centers for Disease Control and Prevention (CDC). Boys are four to five times more likely than girls to be diagnosed with an ASD. And with a 10 to 17 percent annual growth rate, it is the country's fastest growing developmental disability, according to the Autism Society.
A 2005 census study commissioned by the Pennsylvania Department of Welfare's Bureau of Autism Services estimated about 20,000 Pennsylvanians, children and adults, were living with autism, although the study noted that the number was on the conservative side. The bureau now believes that number has grown to between 25,000 and 30,000 state residents.
Meanwhile, the commonwealth is among the states the CDC monitors through its Autism and Developmental Disabilities Monitoring Network. The network's most recently published surveillance year, 2006, estimated that 8.4 per 1,000 children in Pennsylvania had an ASD, a 58 percent increase in total prevalence, from 1 in 190 children in 2002 to 1 in 120 children in 2006.
Minus some details
That's among the lower prevalence rates among the represented states, said Jon Baio, epidemiologist with the CDC's National Center on Birth Defects and Developmental Disabilities and principal investigator for the ADDM. Specifically, one of the factors influencing the numbers is that the ADDM doesn't have access to children's educational records in Pennsylvania, he said.
That said, the state is progressive on the policy end, Mr. Baio said. "A lot of programs have been added there in recent years. That bodes well for children with autism," he said.
Thomas Challman, M.D., a neurodevelopmental pediatrician at Geisinger Health System in Danville who specializes in developmental disabilities and autism, said there's no evidence that ASDs are more common today than they were in the past. However, awareness is much greater among doctors, parents and teachers than it was a couple of decades ago.
"The main factor, probably, is that there's more diagnostical awareness. We're identifying kids earlier," Dr. Challman said. "That goes a long way to contributing to what's popularized as an increase in numbers."
While a clear and definitive cause for autism has yet to be determined, most physicians believe genetic makeup plays a significant role. Children who have a sibling or parent with an ASD are at a higher risk of also having one, and ASDs tend to occur more often in people who have certain other medical conditions or genetic disorders, such as Fragile X syndrome, tuberous sclerosis and Down syndrome.
"Really, where we're sort of at is that the genetic investigations are at their earliest stages," Dr. Challman said. "A variety of genes have shown to be involved in autism. They have to do with how the brain organizes itself. Brain circuitry. But we don't know what they do. We just know they affect autism."
By the numbers
Several hundred different genes, or maybe even thousands of genes, when mutated, can result in autism, said Dr. Challman's colleague, David Ledbetter, Ph.D., a geneticist who serves as executive vice president and chief scientific officer at Geisinger.
"If 10,000 genes are involved in developing normal brain function, something can go wrong with any of those 10,000 genes," Dr. Ledbetter said. "We're still in the relatively early stages of identifying all the genes that play a role. And the relationship of all these genes."
"Once we get the full catalog of genes, it's going to make a lot more sense," he continued. "It'll give us a clue as to how to develop better treatments."
There may also be environmental factors related to the cause of autism, but, as of yet, "there's no clear evidence," Dr. Challman said.
Right now, there are countless studies investigating a number of things that might be a potential environmental contributor, be it prenatally or during the child's early development. The list includes prenatal vitamins, neurotoxins in the air, water and food supply, industrial waste, levels of bisphenol A (BPA) in kids' canned foods, food additives and preservatives and pesticides, said Donna Ferullo, director of program research for the Autism Society.
Even maternal stress and age at the time of the child's birth are being studied, Ms. Ferullo said.
"We live in this soup of low-level exposure. There's so many threats to the developing brain that we weren't exposed to years ago," Ms. Ferullo said. "Environment is suspect, but not clarified. There are numerous environmental factors under investigation. The problem is isolating it."
For years, there have been fears among many parents' groups that vaccines were a potential cause of autism. This was due in large part to a study that came out of England several years ago that implicated the MMR vaccine, which protects against measles, mumps and rubella. That study, though, was later found to be fraudulent, Dr. Challman said.
"So there was some information that was published and it was incorrect and it made people scared," Dr. Challman said. "It's a belief that's not based in science. There's a mountain of evidence that exonerates vaccines."
As the CDC collects more data and enhances its surveillance techniques, researchers will begin to understand more about the disease, Mr. Baio said. One recent development, he said, is the establishment of a controlled testing of three groups - children with autism, children with other developmental disabilities and children who appear to be developing typically.
"We'll be able to compare and contrast across these three groups. The hope of that is we'll identity some factors, be it risk factors, or things that can assist us with identifying children earlier," he said. "Then they can get autism-specific treatments much earlier, which would have a much greater outcome."
"In a lot of ways, we're behind other fields of study," Dr. Challman said. "It is frustrating for families. Sometimes the wheels of science do turn rather slowly, but if we persist, we make progress."
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